When talking to clients about prescribed fire, a question I frequently get asked is, “What about the trees? Won’t the fire hurt the trees?” Good question.

Many of these clients are open to the idea of prescribed fire. Indeed, many of them want to burn, but they don’t want to damage or lose their favorite trees. If this is a dilemma you’re facing, then stick around! In this blog, I will discuss how we navigate tree safety while conducting prescribed burns, and why the safety of a favorite tree shouldn’t be an obstacle to burning.

Are Trees at Risk in a Burn?

Yes, and no. It all depends on the size, age, and species of the tree.

Some tree species, such as oaks, are highly fire-tolerant. This means they have a lot of adaptations that protect them from fire. For instance, oaks have extremely thick bark to protect mature trees from fire. Oaks also have large root systems and root collars deep below ground, which allows them to resprout quickly after fire should seedlings or smaller trees be top-killed. Prescribed fires present very little risk to tree species like oaks. Rarely do controlled burns ever reach the level of heat or size required to truly damage or kill fire-adapted tree species.

Some trees are not highly fire adapted. Trees like maples, ash, elm, cherry, and birch are among the more common hardwoods that are not fire adapted. Their strategies usually involve growing quickly to become large enough to survive small understory fires. These trees are more vulnerable to damage from burning, and the seedlings are less likely to survive a burn. However, fire can still be useful for managing large populations of these species. Prescribed fire tends to burn in patches through forests, meaning it will burn well in some areas and barely burn in others. Therefore, instead of completely destroying all tree seedlings, most prescribed burns will just thin them out. The seedlings that survive have a better chance at survival and better growth conditions. Even fire-intolerant tree species benefit from the light and heat increase created by fire thinning out an understory. Fire could be the key to revamping forest regeneration and growth.

How to Protect Trees Vulnerable to Fire?

But what if you are not managing a woodlot, but rather trying to burn around a few individual trees? For species that are more prone to fire, keeping them safe during a prescribed burn comes down to the process of burning itself. There are many techniques we utilize to keep a fire ‘controlled.’ These techniques involve mowing or digging burn breaks to stop the movement of the fire, using water lines to reinforce breaks, and spraying down areas we don’t want to burn. All of these strategies can be used to protect trees as well.

• We can remove the vegetation or leaf litter around the trunk of the tree. If there’s no fuel around the tree trunk, the fire won’t burn there.

• We can send a water engine ahead of the fire to spray down the area around trees we want to protect. We also spray down the trunks and lower branches of trees. Most prescribed burns are not hot enough to ignite fuel and trees that are dripping in water.

• We can use fire to fight fire. We can lay fire around the tree, let the fuel around the tree burn up while the fire is small, then put it out with water before it starts burning the tree trunk. This creates a ring of burned material around the trees, protecting them when the larger fire moves through. What’s already burned won’t burn again.

• We can backburn through trees. This means we are running the slowest, coolest part of the fire through the trees. Even non-fire-adapted trees are not likely to be hurt by slow moving backing fire.

• We can send a water crew back after a fire passes through to put out any flames that may be starting to threaten trees.

All of these strategies are utilized in various combinations to ensure that we can protect any trees that need protecting during a burn. A skilled burn crew will be able to manage the speed of their prescribed burn, meaning they can take as much time as necessary to ensure a tree is safe from being burned. In fact, these techniques are what we use to protect anything on a prescribed burn unit—trees, brush piles, powerline poles, benches, sheds, etc.

It's important to note that prescribed fire always has an element of uncertainty. Every site will be different with what can be achieved and managed by a burn crew. However, there are many strategies and techniques that we can utilize to ensure our burns are safe, and only burn what we want them to burn. Your best bet is to talk to an experienced prescribed burn boss (we know some good ones!) who will be able to help design a burn plan to achieve your goals and protect your valuable trees. So, if you want to burn, don’t let concerns about protecting trees completely deter you—there are many ways to achieve a successful burn and protect vulnerable trees.